Process for the manufacture of very hard metallic alloys



' Patented Dec. 6, 1927.

. UNITED STATES 1,652,021- PATENT OFFICE.

' nueo 1.01am, on BEBLINJOHANNISTHAL, enmrm.

PROCESS FOR THE MANUFACTURE VERY HARD METALLIG Io Drawing. Application filed August 26, 1821, Serial No. 485,784, and in Germany December 7, 1918.

. (GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L, 1813.)

This invention relates to the manufacture of very hard metallic alloys which approximate the diamond in hardness, but which are not brittle and, therefore, resist crumbling and breakage. The alloys produced by this process are specially adapted fo the manufacture of cutting tools, but are also useful for other purposes.

In alloys of this character heretofore produced there has usually been a certain relationship between the degree of hardness and the amount of carbon contained therein. Steel is usually hardened by chilling, which results in a change of texture and a consequent reduction in its ductility.

There are other alloys, such as silicon carbide and tungsten carbide, of which the degree of hardness is due solely to the amount of carbon contained therein, but which need not be chilled in order to harden them. These alloys, however, are diflicult, if not im ossible, ,to forge, roll or press.

y the process'of the present invention metallic alloys are produced which, in addition to being very hard and ofterin a high resistance to breakage, may be forge ,rolled, pressed or hammered and which are made harder by such operations.

The process consists, essentially, in so com- '30 bining a'metal, such asiron, tungsten, titanium, chromium, or molybdenum, with boron and silicon, during a meltin operation, that the resulting alloy is free of oxygen and of which the degree of hardness 5 maybe increased by a stretching or expanding operation, such as rolling, hammering or pressing, by which action the molecules of the alloy are condensed and changed from a purely coarse granular form to a sinewy or 40 more fibrous form.

Alloys of iron'containing a large proportion of silicon for use in the manufacture of acidroof vessels or the like, as .well as alloys 0 iron and other metals, are known.

" The novelty of the present process, as compared with known processes, resides essentially in the combined additionof silicon and boron to metals such as iron, tungsten, titanium, chromium, nickel or molybdenum.

The process'may be carried out in two ways, a fundamental condition being that the silicon be brought into combination with metals free from oxygen, since otherwise oxidation of the silicon'takes place. care must be taken to exclude carbon from mium or the like) to be combined with the carbon and of Also the mixture or from the finished product. If it be impossible to entirely exclude carbon during the process, for example, where 'the processis carried out in carbon crucibles,

provision must be made for the subsequent elimination of such carbon from the product.

The first mode of carrying out the process consists in melting the boron and silicon and the third metal in a crucible capable of withstanding high temperatures. If, in this operation, carbon is taken up it is afterwards removed by a process of oxidation, such as by embedding the alloy in metallic oxide and then subjecting it to heat. Ad- "antageously, the crucible may be lined with the metal which has the highest fusing point (for example, tungsten), thus insuring the smallest possible absorption of carbon.

The second mode of carrying out the process is based upon the fact that metals having a high fusing point fuse more readily inmetals having a lower fusing point. According to this mode of carrying out the process, the metal (iron, tungsten, chroboron and silicon is first melted and the boron and silicon is then added, after which the combination is completed. The melting should be effected in a smelting furnace capable of being heated to a high temperature. An electrically-heated smelting furnace can advantageously be used for this purpose. The density of the alloy can be increased by subjecting it, while ina molten state, to centrifugal action, which may be effected by the use of a carbon resistance oven mounted to rotate on an axis at a right angle to the axis of' the carbon tube, the entire apparatus being rapidly. rotated on its axis during the melting of the alloy or of the constituents thereof, so that the fused mass is subjected to high pressure and freed of bubbles or pores and its interior texture is homoge- -nized. In this procedure theconstituent which fuses at the lowest temperature (for example silicon) is first melted, the constituent which fuses at the next higher temperature is then introduced into the first constituent, and finally the constituent which fuses at the highest temperature is added.

By carefully conducting these operat ons a protecting but partially fused layer of the most diflicultly fusible constituent is formed on the'inner wall of the crucible and serves to absorb the carbon, so that only a mini- 110.

mum of carbon is absorbed by the core of the mass. Any carbon present in the core of the mass may be removed by any of the well-known oxidation processes, for example, by heating the finished material in a bed of metal oxide to a temperature of from 1000 to 1400 C.

Equal parts of boron, silicon and the third metal for example, 33% per cent of boron,

33 per cent of silicon, and 83 A; per cent' of tungsten) may be employed. Or e ual parts of boron and of silicon and a sum ler proportion of the third metal (for example. 47 per cent of boron, 47 per cent of silicon and 5 per cent of tungsten) may be employed.

The product formed by melting together the three metals has a coarse crystalline structure and is greatly improved by forging, rolling, pressing or hammering, since by such operations the comparatively coarse crystalline grain caused by the fusion of the metals, which would cause the product to be very brittle, is changed into a sinewy fibrous form thus making the product capable of resisting great mechanical strains and stresses.

The process may also be carried out by adding to the boron and silicon two or more metals, for example, tungsten and iron.

I claim 1. The process of manufacturing very hard metallic alloys, which consists in fusing refractory metals, such as iron, tungsten, titanium, chromium, molybdenum with equal parts of silicon and boron, substantially free from carbon and oxygen, and submitting the product to centrifugal, condensing and me ehanical expansive action.

2. The process of manufacturing very hard metallic alloys, which consists in producing an alloy by fusion of refractory metals, suitable for the manufacture of tools with boron and silicon substantially free from oxygen and carbon, and mechanically expanding and condensing the resulting.

product.

3. The process of manufacturing very hard metallic alloys, which consists in fusing refractory metals. while substantially exeluding oxygen, with silicon and boron, and eliminating any carbon existing in the mixture of said materials.

4. The process of manufacturing very hard metallic alloys, which consists in surrounding a mixture of refractory metal with silicon and boron, fusing said mixture, substantially with the exclusion of oxygen, and removing the carbon absorbed during the fusion by oxidation.

5. The process of manufacturing very hard metallic alloys, which consists in surrounding a refractory metal with boron and carbon to a heat suflicient to fuse the three other ingredients, while preventing oxidation of the silicon, and removing any carbon absorbed during the fusion from the finished product.

7. The process of manufacturing veryhard metallic alloys, which consists in su erposing refractory metal on a layer of car on, superposing a mixture of equal portions of boron and silicon upon said refractory metal, exposing the carbon to high heat to fuse the metal and the silicon and boron while preventing oxidation of the silicon, removing any carbon absorbed during the fusion from the finished product, and mechanically expanding and condensing said product.

8. The process of manufacturing very hard metallic alloys, which consists in melting refractory metal, adding boron and silicon free from carbon to the molten metal in the absence of oxygen, producing a mixture of the ingredients, and cooling and condensing the mixture.

9. The method of manufacturing very hard metallic alloys. which consists in interiorly lining a carbon crucible with refractory metal, such as iron, tungsten, titanium, chromium, or molybdenum, placing a mixture of silicon and carbon into the crucible and in contact with said refractory metal, submitting the crucible to melting heat sufficient to fuse the lining and the contents thereof, tempering the resulting mixed metallic product by metal oxide to remove the carbon, and condensing the product.

10. The method of manufacturing very hard metallic alloys, suitable for use as tools, which consists in interiorly lining a carbon crucible with refractory metal, such as iron,

tungsten, titanium. chromium or molybdenum, placing a mixture of equal parts of silicon and carbon into said crucible In contact with said metal, submitting the crucible specification.

HUGO LOHMANN. 

